From a3a837d8081f7b384c4f2ab0a9e98ddbc4806b7f Mon Sep 17 00:00:00 2001
From: Maurizio De Santis <desantis.maurizio@gmail.com>
Date: Thu, 7 Feb 2019 09:56:02 +0100
Subject: [PATCH 1/2] Exclude line item additional taxes from unit cancel
 adjustment amount

Fixes #3068. It takes into account the line item taxes amount during
calculation of line item amount on line item cancellation.
---
 core/app/models/spree/unit_cancel.rb       |  3 +-
 core/spec/models/spree/unit_cancel_spec.rb | 41 ++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/core/app/models/spree/unit_cancel.rb b/core/app/models/spree/unit_cancel.rb
index 909f3c136d5..b5d305c0380 100644
--- a/core/app/models/spree/unit_cancel.rb
+++ b/core/app/models/spree/unit_cancel.rb
@@ -34,6 +34,7 @@ def adjust!
   # This method is used by Adjustment#update to recalculate the cost.
   def compute_amount(line_item)
     raise "Adjustable does not match line item" unless line_item == inventory_unit.line_item
-    -(line_item.total.to_d / line_item.inventory_units.not_canceled.reject(&:original_return_item ).size)
+
+    -((line_item.total - line_item.total_before_tax).to_d / line_item.inventory_units.not_canceled.reject(&:original_return_item).size)
   end
 end
diff --git a/core/spec/models/spree/unit_cancel_spec.rb b/core/spec/models/spree/unit_cancel_spec.rb
index 0093a7e3e2e..a5f52e21af6 100644
--- a/core/spec/models/spree/unit_cancel_spec.rb
+++ b/core/spec/models/spree/unit_cancel_spec.rb
@@ -76,5 +76,46 @@
         expect(line_item.reload.total.to_d).to eq(0)
       end
     end
+
+    context 'when line item has additional taxes' do
+      let(:world_zone) { create(:zone, :with_country) }
+      let(:tax_category) { create :tax_category }
+      let(:product) { create :product, tax_category: tax_category }
+      let!(:additional_tax_rate) do
+        create(
+          :tax_rate,
+          name: 'Additional tax',
+          tax_categories: [tax_category],
+          zone: world_zone,
+          included_in_price: false,
+          amount: 0.15
+        )
+      end
+      let(:shipping_category) { create :shipping_category }
+      let(:shipping_method) do
+        create :shipping_method,
+               cost: 8.00,
+               shipping_categories: [shipping_category],
+               tax_category: tax_category,
+               zones: [world_zone]
+      end
+      let(:shipping_address) { create :address, country_iso_code: world_zone.countries.first.iso }
+      let(:order) do
+        create(
+          :order_with_line_items,
+          ship_address: shipping_address,
+          line_items_attributes: [{ product: product }]
+        )
+      end
+      let(:line_item) { order.line_items.first }
+      let(:inventory_unit) { line_item.inventory_units.first }
+
+      before { order.recalculate }
+
+      it 'does not include line item additional taxes' do
+        expect(line_item.additional_tax_total).not_to eq 0
+        expect(subject).to eq(-5.0)
+      end
+    end
   end
 end

From d822a085e61880a5dcfa355da08457ccfa210de7 Mon Sep 17 00:00:00 2001
From: Maurizio De Santis <desantis.maurizio@gmail.com>
Date: Thu, 7 Feb 2019 09:58:30 +0100
Subject: [PATCH 2/2] Refactor Spree::UnitCancel#compute_amount

Related to #3068. In order to keep code consistency, I made a
refactoring along the same lines of
`core/app/models/spree/calculator/returns/default_refund_amount.rb`,
which performs a similar calculation.
---
 core/app/models/spree/unit_cancel.rb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/core/app/models/spree/unit_cancel.rb b/core/app/models/spree/unit_cancel.rb
index b5d305c0380..d54c78ac614 100644
--- a/core/app/models/spree/unit_cancel.rb
+++ b/core/app/models/spree/unit_cancel.rb
@@ -35,6 +35,16 @@ def adjust!
   def compute_amount(line_item)
     raise "Adjustable does not match line item" unless line_item == inventory_unit.line_item
 
-    -((line_item.total - line_item.total_before_tax).to_d / line_item.inventory_units.not_canceled.reject(&:original_return_item).size)
+    -weighted_line_item_amount(line_item)
+  end
+
+  private
+
+  def weighted_line_item_amount(line_item)
+    line_item.total_before_tax / quantity_of_line_item(line_item)
+  end
+
+  def quantity_of_line_item(line_item)
+    BigDecimal(line_item.inventory_units.not_canceled.reject(&:original_return_item).size)
   end
 end